The current multiple antenna technique mainly includes two forms: a smart antenna system, and a Multiple-Input Multiple-Output (MIMO) antenna system. In the MIMO antenna system, multiple antennas are used to suppress channel fading or to improve channel capacity, which may provide spatial multiplexing gain and spatial diversity gain for the system, wherein spatial multiplexing technology may greatly improve the channel capacity and spatial diversity may increase reliability of a channel and decrease bit error rate of the channel. The MIMO antenna system mainly achieves diversity gain dependent upon independence of spatial channel fading characteristics on different antenna pairs. Therefore, larger antenna element spacing is needed in the MIMO antenna system.
The smart antenna system mainly performs signal processing dependent upon high dependence between array elements to achieve beam forming. Therefore, smaller antenna element spacing is needed in the smart antenna system, which is set to ½ wavelength while applied currently in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system in a third generation mobile communication system. For example, in the TD-SCDMA system, all elements of a smart antenna array (assume a number of the elements is N, where N is a positive integer) employ the same vertical polarization. Each antenna element spacing is ½ wavelength. The N antenna elements act together on beams from respective directions to perform spatial filter. Narrow beams with high gain is point to the direction of a served user, and null is pointed to the direction of interference, which increase output signal-to-jamming ratio of the array and reduce the interference inside the system while improving the anti-interference capability and the coverage capability of the system. However, since a common channel and a broadcast channel (or a MBMS service) do not have a downlink beam forming gain, there is a significant difference between the coverage capability of the common channel and the broadcast channel (or the MBMS service) and that of a channel for a general service, so that the actual coverage range of the network or the MBMS service is smaller than that of a service channel, which results in that advantages of the performance of the smart antenna may not be presented sufficiently. Although interference of the common channel in a multi-frequency cellular network may be reduced to some extent by the multi-frequency networking technique, the actual network indicates that the coverage capability of the common channel is still weaker than that of the service channel.